Since the first CRT-based oscilloscope (as well as other real-time test and measurement equipment) was invented users have been generating and annotating hardcopies of screen images as part of a reporting feature. Often a user not only wanted to memorialize a displayed waveform, but also wanted to make various notes to point out portions of the waveform, or to record other information with the waveform, perhaps for a laboratory notebook or the like. In the early days of true analog oscilloscopes, an instant camera (e.g. Polaroid Instamatic) was commonly used to merely take a picture of the oscilloscope display. The images produced by these cameras would then typically be glued into a lab-notebook, along with annotation, both around, and sometimes on the image. While this allowed for a user to have a record of the waveform and various notes related thereto, this tedious method has many obvious drawbacks. First, the image clarity is dependent on the camera used. Additionally, the need to paste the image, and then write on and around the image in undesirable, perhaps producing noted that are imprecise or difficult to read. Furthermore, it was difficult to share the recorded information with others. Finally, if an error was made, or a change to the annotation was desired, a new picture had to be taken. If the waveform was one that could not easily be reproduced, taking another picture may have been impossible.
With the advent of Digital Storage Oscilloscopes (DSOs) the Polaroid camera was generally discarded in favor of electronic means of image capture. Early DSOs were equipped with GPIB or RS232 ports. Data could be output via these ports to a host computer, which would in turn capture an image of the display. Some later oscilloscope models included built-in Mass-Storage devices, including the Floppy Drive, hard drives, and more recently USB-based ‘flash drives’. The later could then be used via ‘Sneaker-Net’ to transfer the screen image to another electronic device by physically moving the USB drive.
In each of these situations, once the image information was captured on the oscilloscope, a common workflow involved transferring the image into a host computer for storage and display using one of the above methods, and then loading the image into a picture editor type of software package so that various annotations could be added to the image before pasting the annotated image into a word-processor file in order to generate a report, or to be saved as part of an electronic lab notebook or other historical record.
One attempt at allowing a user to return an oscilloscope to a prior state was the LeCroy LS-140 oscilloscope. In a snapshot mode, acquisition data is stored to a storage device, and returned to channel acquisition memory as desired. The oscilloscope would therefore be in the same state as when it acquired the data. However, no graphical data is stored. Rather, any graphics is regenerated based upon the returned acquisition data.